I have many sites on many different TLDs, and I'm virtually certain that Google prefers some global TLDs over others. From what I can make out, .COM, .NET and .ORG have roughly equal value, .US domains are a bit lower, and .BIZ are almost impossible to get ranked. I've never used a .INFO domain so I can't place them, but my hunch is that they are treated as lesser than .COM, .NET and .ORG.
I've been thinking this same thing but by time you find a good .com generally you have to add too many characters to the word to stay very targetted at specific words.